1. Field of the Invention
The present invention relates to radio telephone apparatus which are mounted and used on vehicles such as automobiles and, more particularly, to radio telephone apparatus which include a portable radio device removable outside the vehicles.
2. Description of the Related Art
Automobile telephone devices are known as radio telephone apparatus used in vehicles such as automobiles. In the automobile telephone device, a dial signal and a communication signal are transmitted from a handset disposed at the seat of the automobile via a transceiver installed, for example, in the trunk to the base station through which the telephone device makes telephone communication with a remote cable telephone or a remote radio telephone apparatus. According to this structure, the handset at the automobile seat cannot be removed from the transceiver in the trunk, so that the handset cannot be moved outside the automobile to make telephone communication.
Radio telephone apparatuses have been developed which are capable of making telephone communication either inside or outside the vehicle. FIG. 9 is a block diagram of such conventional radio telephone apparatus which includes a portable radio device 1, a vehicle-mounted additional unit 2, a handset 3 and a handset cradle 4.
The radio device 1 is fixed usually in a recess in the additional unit 2. A chargeable battery 11 is charged with a charging current which flows from the automobile battery (not shown), via a power cable 20, a connector 21 of the unit 2, and a connector 10 mounted on the back of radio device 1.
The radio device 1 includes a telephone mouthpiece 12 and a telephone earpiece 13 for telephone communication, a control panel 14 including dial keys, etc., operated for transmitting and receiving calls, a telescopic antenna 15, and a transmitter-receiver, a voice circuit, etc., provided therein.
The additional unit 2 includes an antenna cable 22 which is connected to a transmitter-receiver antenna 5 fixed outside the vehicle, and a voice cable 23 through which a communication signal is transmitted and received by the transmitter-receiver in the radio device 1 via the handset cradle 4 to and from a telephone mouthpiece 30 and a telephone receiver 31 of the handset 3.
The handset 3 has a curl cord 32 which transmits a telephone communication signal. When the handset 3 is placed on the cradle 4, valleys (not shown) in the handset between the telephone mouthpiece and earpiece 30 and 31 are engaged with resilient pawls 40 and 41 of the cradle 4 for fixing purposes.
In operation, when the antenna 5 fixed to the vehicle receives an incoming signal from a calling telephone apparatus via the base station (not shown), the received signal is delivered via the antenna cable 22, and connectors 21, 10 to the transmitter-receiver of the radio device 1. The transmitter-receiver demodulates the received signal and generates a ringing tone from a sounder (not shown) of the radio device 1 to call the user. When the user operates an off-hook switch (not shown) provided at the control panel 14 of the radio device 1 in response to the ringing tone, a telephone communication path is established between the radio device 1 and the calling telephone apparatus via a radio link. Thus when the handset 3 is lifted from the handset cradle 4, telephone communication is enabled through the telephone mouthpiece and earpiece 30 and 31 of the handset 3.
The voice signal from the telephone mouthpiece 30 of the handset 1 is delivered as a modulation signal for the carrier signal through the curl code 32, cradle 4, voice cable 23, connector 21 of the additional unit 2, and connector 10 of the radio device 1 to the transmitter-receiver of the radio device 1. The modulated output from the radio device 1 is transmitted via the connectors 10, 21, and antenna cable 22 from the antenna 5.
If the off-hook and dialing operations are performed at the control panel 14 of the radio device 1 for transmitting a call signal from the vehicle, the dialing signal is delivered as a modulation input to the transmitter-receiver where it is converted to a high frequency signal and transmitted via connectors 10, 21 and antenna cable 22 from the antenna 5. A telephone communication path is established by the off-hook response of the called apparatus as in the reception of the call.
When the radio device 1 is removed from the additional unit 2 and used outside the vehicle, the antenna 15 of the radio device 1 is set in a transmission-reception enable state by extending the antenna 15 to thereby transmit and receive calls directly to and from the base station. When a communication path to the called apparatus is established, telephone communication is possible using the telephone mouthpiece and earpiece 12 and 13.
As just mentioned above, telephone communication is possible both inside and outside the vehicle according to this arrangement.
Since the handset 3 includes only the telephone mouthpiece and earpiece, the off-hook and dialing operations must be performed at the control panel 14 of the radio device 1. Therefore, the radio device 1 and handset 3 are required to be disposed close to each other.
Since many drive meters or the like are disposed in the vicinity of the driver seat of the automobile, it is often difficult to select a space where the radio device 1, additional unit 2, handset 3 and handset cradle 4 are installed. Even if they are installed, they may hinder the driver's operations, so that there is nothing for it but to select an installation place inconvenient to operate the telephone apparatus.
It is therefore an object of the present invention to provide a radio telephone apparatus which occupies a small installation space in a vehicle such as an automobile.